1. Field of the Invention
The present invention generally relates to a particulate filter regenerating device for a particulate filter used to after-treat the exhaust gas of engines, especially diesel engines. The present invention also generally relates to an engine exhaust gas cleaning device that utilizes such a particulate filter regenerating device.
2. Background Information
Diesel particulate filters are particulate matter collecting devices comprising a honeycomb monolith made of ceramic or the like. Diesel particulate filters are generally used to remove particulate substances (hereinafter called “particulates”) from the exhaust gas discharged by diesel engines. During operation, particulates gradually accumulate in the diesel particulate filter. Eventually, the quantity of accumulated particulate matter exceeds an allowed quantity and clogging occurs. Once the particulate filter is clogged, this causes the exhaust pressure to rise and the operation of the engine to be adversely affected. As a result, it is necessary to periodically remove the accumulated particulate matter from the particulate filter so that clogging does not occur.
One known regeneration process for removing particulates from diesel particulate filters is disclosed in Japanese Laid-Open Patent Publication No. 7-034853. The regeneration process of this publication proposes to raise the temperature of the exhaust gas above normal and feed the exhaust gas into the filter, thus heating and combusting the accumulated particulate matter.
This publication discloses that the time to regenerate a diesel particulate filter is determined by calculating the pressure difference across the diesel particulate filter by measuring the pressure inside the exhaust passage at the front and rear of the filter and estimate the quantity of accumulated particulate matter based on the calculated pressure difference and the exhaust gas flow rate (which can be calculated based on the intake air flow rate, etc.). When the estimated quantity of accumulated particulate matter reaches a prescribed quantity, the system determines that it is time to regenerate the filter.
When it is determined that it is time to regenerate the diesel particulate filter, the diesel particulate filter is regenerated by executing control that raises the temperature of the exhaust gas above what is normal and heats the accumulated particulate matter to or above a combustion temperature.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved particulate filter regenerating device. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.